Very satisfied with this cleaner. I initially bought the Dolphin Premier based on reviews on Amazon and elsewhere. It did an amazing job cleaning the pool floor. But it did not climb walls and clean the waterline in my pool. I feel this is very pool dependent. Every pool is different. Since it did such an amazing job with the floor, I debated just keeping it and doing the walls manually like before. Particularly since the unit is quite big and heavy and a pain to repack and ship back. But then, I had not paid a premium for a robot that only cleans the floor. Finally decided to return the Premier and get the Sigma, which is more expensive but has some technology which I thought might help it climb the walls better. Glad I made the switch.
The Sigma does just as well cleaning the pool floor. But it is also able to get to the waterline in my pool and clean it. At least half the time it tries. That's fine as long as it eventually gets to the entire waterline. Whether it succeeds in an attempt to get to the waterline, I think depends on the angle it approaches the wall, how heavy it is at the time and other variables.
In addition to being able to climb walls, I found the Sigma better than the Premier in some other ways. I much prefer the top access for the filters on the Sigma compared to the bottom access with the Premier. Both units leak some dirt back into the pool when you take them out of the water, but seems to be much less with the Sigma. The ultra fine filters on the Sigma are much bigger with the Sigma. While the leaf bag idea on the Premier seemed good, in practice I found it a hassle. Because of the way it is "crammed" into the unit, it really has no space to expand fully (although it does pick up a fair amount of leaves). It is also a bit of a pain to clean and reinstall. The large filters on the Sigma pick up a comparable amount of leaves, and are much easier to take out, clean and put back in. The Sigma has a smartphone app which notifies you when a cleaning cycle is done. You could start another cycle remotely if you wanted. It also allows you to manually drive the robot. I have not tried it but seems to be sluggish based on other reviews. I personally don't feel the need to use this feature.
So why 4.5 stars? I think it is a bit too expensive. It also does not seem to have any smart mapping capabilities. Seems to just randomly move around the pool. Eventually gets all or most of the pool in a cleaning cycle, so I suppose it doesn't matter. By comparison my home robot vacuum which is much cheaper than the pool robot can map and remember every detail of every room of a two story house, and is very methodical in the way it goes about cleaning. One would think mapping a pool would be simpler. Should have an option to update the firmware on the unit as improvements are made to the software. Again, my much cheaper vacuum robot has this capability.
One last point - the return process for the Premier was very smooth.
All in all, highly recommended. Now it just has to stand the test of time. I bought extended warranty, just in case.

Couple months back a decided to try a robotic vacuum because my pop ups just weren't cutting it. I initially purchased the Dolphin Quantum and was pleased at its performance. What I didn't like was how it would get stuck on my drain covers and be dead in the water after that. I couldn't just set it and forget it like I had hoped. So I did a little more research and decided to send it back and upgrade to the Sigma. I had hoped the independent drive tracks would allow it find its way off the drains. Nope! The Sigma does do a really good job at cleaning the bottom and sides of my pool but not any better then the quantum. And I'd say the Quantum is actually better at cleaning the water line tile. The Sigma gets up to water line and pretty much just keeps scrubbing one area where the Quantum had side jets which allowed it to move sideways along the water line scrubbing tile as it goes. All in all the Sigma does a really good job but wouldn't say its worth the extra money. If I had to do it over again I would have kept the Quantum. Both are very easy to use and to clean.

The vacuum is amazing BUT"¦ like the other reviewers said it gets stuck on the grate of the drains at the bottom of the pool so then you have to push them off and who knows how long they were stuck there. How much of your pool was cleaned before they got stuck. Other than that the vacuum is amazing it cleans up the sides of the walls. It climbs the stairs well, and the Baha shelf. Too bad it can't climb up into the hot tub then it would be exceptional.
Since purchasing this vacuum our pool has been very clean looking. You still have to scrub some spots that are hard for it to get too. But it cleans 99% of the pool.

1) It gets hung up on the main drain at least once per cleaning cycle - like a turtle on its back. The tracks are on the sides, and brushes are front and back, with nothing moving in the entire central under-belly. If the robot drives up on the main drain dead-on, it gets stuck and can't get itself free. A light tug on the cord sets it free and it continues without any problems. However, when running unattended, this has been a big issue. It got stuck at the beginning of the cycle one time, and I didn't notice until near the end of its routine. There are a few devices on the market that make a ramp (like a ring around the drain), and clips that create a dome over the drain cover. These options are ~$50, last only a few years, may be difficult to assemble, and reviews are generally horrible. But someone posted an interesting solution, and I've been trying to make it work. That is, screw a 1" PVC cap (with stainless screw & washer) to the main drain cover to create a 'dome'. It should lose balance when it tries to climb the dome, causing at least one track or brush to contact the pool bottom. My first attempt didn't work, because I used a shallow cap. My next attempt will be to use a cap & pipe (as an extension). Making it taller should do the trick. Associated problems were:
- weighting my self down so I could stay on the bottom (weight vest + weights on a tool belt + mask & snorkel
- pre-drilling the hole for the screw. I held onto a wood spade bit by hand, and worked it to get a hole started
- staying on the bottom while applying force to pre-drill, then use the screw driver. I used a garden claw to hook onto the main drain with one hand, while working the tool with the other.
- Interesting experience . . . but totally doable. Just make sure you have someone spotting you and extending a pole for you to grab onto when you come up for air. Or . . . find someone with scuba gear :)
2) The remote (blue tooth with smart phone) works, and I've used it successfully to get a few spots the robot missed (especially after it gets hung up on the main drain). However, response time between action & reaction is poor, and I usually over-compensating on turns. It's frustrating trying to get the thing pointed in the right direction . . . but it gets the job done . . . eventually.
3) No caddie. I wrote to the manufacturer and didn't get a reply. I eventually put the power supply in a patio box to keep it out of the weather, and I leave the robot in the water all the time, so not having a caddie hasn't been a problem.

All-in-all, I'm very happy. The pool hasn't been this clean - ever!

On the plus side:

4) Its completely self-contained.
5) Filters only need to be cleaned every couple/few of weeks. Cleaning is very simple because filters are top-loaded & easy to remove. Then use garden hose to clean.
6) No suction hose to lay out and prime.
7) Skimmer baskets don't get plugged, thereby creating reduced pressure and suction on the vacuum hose.
8) No debris goes into the filter, so I backwash less often - less water loss, and hence, fewer chemicals lost.

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*** 2 Month Update ***
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My biggest complaint was (#1 abv.) the robot getting hung up on the main drain. Perhaps I wasn't being fair to the robot, and should clarify that this problem is not specific to this robot, since many people experience the same issues with other robots. Abv. I said I'd try a taller 'post', which I did, and it didn't solve the problem. The post I bolted onto the main drain cover was ~2" tall, but the robot would happily climb on top of it, then balance itself perfectly with all tracks and brushes suspended - not in contact with the bottom. I think the handle is designed to balance it. Anyway, I thought about modifying the bottom of the robot, but didn't want to void the warranty. In the end, I decided to lower the main drain cover by building a custom cover out of a 10" wide x 1/2" thick HDPE cutting board ($6 from the Job Lot). This solution has been working flawlessly for a week now.

I was concerned about buying this machine because my pool has infinity edges on all four sides that are about 18 inches above ground. I feared that the robot would see it as as step and fall over the edge. I also wanted it to clean the catchment basin and I was afraid that it couldn't do it because it's pretty shallow. No worries on either count. It worked perfectly the first time in both areas. The gross catchment basin looks like new and the spots on the pool floor that even my floor system couldn't drive into the drain are now clean. So simple and easy to use. You put into the water and push the button and go away. The app was super simple to install and it just works. I like that it tells me how far into the cleaning cycle the machine is and when it will be finished. Removing the filters, spraying them out, and putting them back into the machine couldn't be easier. I would compare this machine to a Dyson vacuum cleaner in terms of ease of use and good design. My only warning is that it's heavy. I'm a small female in my mid 60s and I can lift it in and out of the pool and carry it back to the garage...but if it were any heavier I couldn't do it. So glad I bought the Dolphin Sigma even with the high price. It gets the pool and catchment basin so much cleaner than I could possibly do with my pool brush. The price of the robot is just a fraction of what you already spent on building your pool, and it makes pool maintenance so much less time-consuming and in my case - it's now feasible to keep the catchment basin as clean as the pool.

A few days later: I've changed my review to 4 stars. Today, the robot did weird things in the catchment basin. It turned upside down twice and I had to rescue it. This could be because this area of the pool is narrow. And - it started squeaking really loudly when it cleans the water line! I don't see anything stuck anywhere. It's odd that this would happen after only a week of use. I saw online that someone else had this problem and oiled something...not sure I want to be taking the robot apart so early in the game.

I'm still happy with the way it cleans the main pool. Will have to keep an eye on it while it's in the catchment basin. Will update review later...

Verdict: Works great on my infinity pool. Goes all the way up the sides and doesn't fall over. Just need to brush off the ledge and stairs and it takes care of the rest. The Dolphin cleans the catchment basin well except for two corners, but need to keep an eye on it because it can end up upside down. To be fair, it really wasn't meant to clean such a shallow and narrow space, so I'm OK with this. Really glad I have the Dolphin to help me keep my pool clean. Saves me TONS of time.